Hydrogenation of tartaric acid esters to erythritol



Patented Oct. 16, 1951 HYDROIGENATION OFJTA'RTA'RIC ACID ESTERS'TO ERYTHRITOL :NelsonRichardTrer-mer and'Frederick-A; Bacher, I Westfield, N. ,J.,..assignors to =Merck :& 00., Inc., .Ra-hway,,N.,.J., aoorporation. of New-Jersey "No Drawing. Application November 9, 1948, :Serial No. 59,184

.,6-C.laim.s. (01.260-4535) vThis invention relates to the preparation :of

. therapeutical; products: and, more. particularly; to .the, preparation oferythritol, an intermediate in .the preparation of tetranitrate of. erythrit'ol 11seiul as-a vasodilator in the treatment :of heart an- :ments.

..It has been-proposed to :prepare the tetranitrate of erythritol. from butadiene-by {a long "series-f stepsiout .such a method-is very. .costly and requires .sk-illed -lab.0r..and expensive. equip- .ment.

' We have .now tonnddihatitis possible to obtain erythritol in excellent yield by reducing a dialkyl ester of tartaric acid under closely controlled conditions. .Whepparryingnutthisprocess, in accordance with our invention, a solution of dialkyl ester of .tartaric acid in a .lower aliphatic alcohol is brought intocontact with a suitable:hydrogenation catalyst suchas black-copper-chromium oxide, and hydrogenated under high pressure of at least 3500 lbs. p''r'square inch and atga temperature of about 125 to'"200 C.

It is essentialthatthe hydrogenation be carried outat a high pressure preferably, of5000 lbs. or more as almost no reaction will take place at 2000 lbs. pressure, orrless. The reduction may be carried-out atzabout 125.to 200 C. but the preferred range is150-'175 C. The lower temperature requires longer reduction; periods while temperatures of 200 C; or-more result in the hydrogenolysis or erythritol. It is equally essential: to employ relatively large amounts of catalysts, preferably m by-weight ofthe amount-of ester used. High ratios of catalyst are necessary for obtaining-high. yields as; the :catalysts usually lose some .of their activity :during the process of hydrogenation.

The reaction-may be "represented :by-the following equation:

002R onion CHOH Oil-chromium oxide CHOH .HOH vAct-200 o. rnon I alcohol 002R ,GHiOH The following examplesillustrate-methods of carrying-out thepresent invention, but it'ds to be understood that these examplesare given byway of illustration and not of limitation.

' EXAMPLE ,1

'followed by the removal of-the d and 1' isomersas" the potassium salts and precipitation of lead meso=tratrate (Beilstein; III, 529; 4th-ed;, 1921) .Esterifiwtionof the-lead saltwasefifected through the .use. of'ethanolic hydrogen chloride. The crystalline diethylmeso-tartrate was isolated and purified. The purified ester melted at 54-56 C.

Black copper chromium oxide catalystwas prepared according to the procedure outlined on page 13 of Adkins, Reactions of Hydrogen with Organic Compounds over Copper-chromium Oxide and Nickel Catalysts, the" University of Wisconsin, Press (1937).

The hydrogenation bombused was made ,of alloy steel, capable ofbeing heatedand withstanding high pressures. The reaction mixture wasrpla-ced in a copper liner, which was then placed. in ,the bomb. ...To .thebomb capwaslattached-a line from a source of high-pressure hydrogen and a pressure gauge. Thetemperature of the bomb contents was held constant by therinostatic control.

After carefully cleaning the copper liner, 2.5 gm. of the copper-'chromium"'o'xide catalyst, .5 gm. of diethyl meso-tartrate, and 107 cc. of absolute methanol were charged. Hydrogen gas was 1 ture was allowed to drop'to' =while shaking continued; the to 4520lbs. per square inch.

then introduced until a pressure square inch at 33 of 3580 lbs. per

the same, indicating-the absence of leaks.

The temperature was then raised to 164 ;C.

over a period of one hour, and a pressure of 5120 was maintained at -168" while the bomb was subjected to continuous shaking. The pressure varied from about 5000 to about 5100 lbs. per square inch. The tempera- C. over one hour, pressure dropped The bomb. was. then allowed to cool overnight to 29 C. without shaking, the pressure at this temperature was.:-3400 lbs. per square. inch.

The bomb was then vented to release hydrogen, opened, and the contents were removed. The mixture was heated to boiling and filtered -hot to remove the catalyst. The filtrate wasconcentrated on'a steam bath to about 10 cc. and then was cooled and agitated to induce crystallization of meso-erythritol. A large volume of diethyl ether =.was.addedto complete the crystallization, and the solid was filtered and-washed withethanoland ether? There was-obtained 1.8 gm. (60.8%) of meso-erythritol. v

' The combined fi-ltrate and washings were evaporated to dryness on: a steam of syrup remained. I The syrup was dissolved in hot eth-anoland cooled. additional-Olden C. was attained. After stand-' .ing one-half hour, the gauge reading remained bath, and 1.0 gm.

of meso-erythritol crystallized, to give a total yield of 1.95 gm. (65.8%).

The combined filtrate and washings were evap orated to dryness on a steam bath. and 275 cc. of hot ethyl acetate were added. The solution cooled and an oil separated and was removed. The ethyl acetate layer was evaporated to dryness, and 0.2 gm. (4%) of unchanged diethyl meso-tartrate remained.

The oil layer was distilled in vacuo, and the fraction boiling at 80-100 C./l-4 mm. was collected. There was obtained 0.65 gm. (22%) of isomerized erythritol. Thus an overall recovery of 2.6 gm. (8'7 .8%) of erythritol was obtained, and 0.2 gm. (4%) of unchanged starting material was recovered.

The meso-erythritol melted at 118-122 C., and a solution in ethanol showed no rotation. Anal. Calcd. for C4H10O4: C-39.3; H-8.25. Found: C39.9; H-8.l3.

The isomerized erythritol was characterized as the dibenzal derivative: M. P. 2l6-218 (3.; mixed M. P. with dibenzal d-erythritol 213-218 (3.; mixed M. P. with dibenzal meso-erythritol (M. P.

195-198 C.) l85-l86 C. Anal. Calcd. for C1sH1aO4. C-'72.5; H-6.05. Found: (J-72.3; H-6.2.

EXAMPLE2 The following table shows the results of several experiments carried out under varying conditions and with varying starting materials.

being present in an amount in exces of about by weight of said tartaric acid ester, and recovering erythritol from the resulting mixture.

2. The process of preparing erythritol in high yields by hydrogenation of tartaric acid esters, which comprises, subjecting a solution of an ester of tartaric acid selected from the group consisting of dirnethyl tartrate and diethyl tartrate in a lower aliphatic alcohol selected from the group consisting of methyl alcohol and ethyl alcohol to the action of hydrogen, said hydrogenation reaction being carried out at a temperature within the range of 125-200 C., and at a pressure of at least 3500 pounds per square inch in the presence of black copper-chromium oxide catalyst, said catalyst being present in an amount in excess of about 50% by weight of said tartaric acid ester, and recovering erythritol from the resulting mixture.

3. The process of preparing erythritol in high yields by hydrogenation of tartaric acid esters, which comprises, subjecting a solution of an ester of tartaric acid selected from the group consisting of dimethyl tartrate and 'diethyl tartrate in a lower aliphatic alcohol selected from the group consisting of methyl alcohol and ethyl alcohol to the action of hydrogen, said hydrogenation reaction being carried out at a temperature within the range of 150-l75 C., and at a pressure of at least 3500 pounds per square inch in the presence of black copper-chromium oxide catalyst, said catalyst being present in an Table Hydrogen Hvdro- Per cent Temp" g g g' genaxg' gg unre- Nature and amount of Reactant Solvent s Sq in at tion of acted products (based onstartmg Re'act'ion tune, starting reactant converted) Temp hours Reactant 1 Dimethyl meso-tartrate. methanol. 172 5,100 5.5 0.5 12.5 64.5% meso-erythritol (M P. 120 0.); 32% isomerized erythritol syrup. 1

2 Dimethyl meso-tartratc -do 165 5,100 5.0 0.5 22.5 72% meso (M P. 110' (0.); 28% isomerized erythritol 3 Dunethyl meso-tartrate. ethanol 165 5,100 6.0 0.5 12 73% meso; 23% isomenzed erythritol syrup.

4 Dlrnethyl mesotartratanu methanoL 165 2,000 6.0 0.5 100 No reduction; catalyst changed to red inactive orm.

5 Diethyl meso-tartrate .do 165 5,100 4.5 0.5 10 62% meso (M P. 121 C); 35% isomerized erythritol syrup. Q

0 Dlethyld-tartrat-e do 165 5,100 4.0 l.l5 35 97% partially isomerized ccrythrltol (M. P. 88-90 7 Dlethyld-tartrate do 165 5,100 5. 0.5 partially isomerizcd d-erythritol (M. P. 87.5- 885 C 8 Dlethyld-tartrate. ,do 165 5,100 5.0 1.0 20 65% partmlly iscmerized d'crythntol (M. P. 8788 0.); 16% isomerized erythritol syrup.

9 Diethyld-tartrate none Z 165 5.100 13.5 0.2 96 100% isomerized erythritol.

1 a] "=3.9 (6% solution in water). Accepted value for derythrltol in water: =4.3.

I u]p"=3.9 (6% solution in water). 5 The catalyst specimen used Modifications may be made in carrying out the present invention without departing from the spirit and scope thereof and the invention is to be limited only by the appended claims.

We claim:

1. The process of preparing erythritol which comprises, reacting a solution of a dialky est of tartaric acid in a lower aliphatic alcohol with hydrogen, said hydrogenation reaction being carried out at a temperature within the range of -200 C., and at a pressure of at least 3500 pounds per square inch in the presence of black copper-chromium oxide catalyst, said catalyst 75 per square inchin the presence in this experiment was the same specimen previously used for the reduction in experiment 6, above, and was merely washed with methanol between experiments.

amount in excess of about 50% by weight of said tartaric acid ester, and recovering erythritol from the resulting mixture.

4. The process of preparing erythritol in high yields by hydrogenation of tartaric acid esters, which comprises, subjecting a solution of dimethyl tartrate in a lower aliphatic alcohol selected from the group consisting of methyl alcohol and ethyl alcohol to the action of hydrogen, said hydrogenation reaction being carried out at a temperature within the range of 1'75" C., and at a pressure of at least 3500 pounds of black copperchromium oxide catalyst, said catalyst being present in an amount equivalent to about 50- 100% by weight of the weight of said dimethyl ester of tartaric acid, and recovering erythritol from the resulting mixture.

5. The process of preparing erythritol in high yields by hydrogenation of tartaric acid esters, which comprises, subjecting a solution of diethyl tartrate in a lower aliphatic alcohol selected from the group consisting of methyl alcohol and ethyl alcohol to the action of hydrogen, said hydrogenation reaction being carried out at a temperature within the range of 150175 0., and at a pressure of at least 3500 pounds per square inch in the presence of black copper-chromium oxide catalyst, said catalyst being present in an amount equivalent to about 50 to 100% by weight of the weight of said diethyl ester of tartaric acid, and recovering erythritol from the resulting mixture.

6. The process of preparing erythritol in high yields by hydrogenation of tartaric acid esters, which comprises, subjecting a solution of diethyl-meso-tartrate in a lower aliphatic alcohol selected from the group consisting of methyl alcohol and ethyl alcohol to the action of hydrogen,

6 said hydrogenation reaction being carried out at a temperature within the range of 150-175 C., and at a pressure of at least 3500- pounds per square inch in the presence of black copperchromium oxide catalyst, said catalyst being present in an amount equivalent to about to by weight of the weight of .said diethylmeso-tartrate, and recovering meso-erythritol from the resulting mixture.

NELSON RICHARD 'IRENNER. FREDERICK A. BACHER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,079,414 Lazier May 4, 1937 2,091,800 Adkins, et a1. Aug. 31, 1937 2,271,083 Lorand Jan. 27, 1942 OTHER REFERENCES Jour. Am. Chem. Soc., vol. 70, No. 9, September 1948 (Adkins and Billica), pages 3121-3125. 

1. THE PROCESS OF PREPARING ERYTHRITOL WHICH COMPRISES, REACTING A SOLUTION OF A DIALKYL ESTER OF TARTARIC ACID IN A LOWER ALIPHATIC ALCOHOL WITH HYDROGEN, SAID HYDROGENATION REACTION BEING CARRIED OUT AT A TEMPERATURE WITHIN THE RANGE OF 125-200* C., AND AT A PRESSURE OF AT LEAST 3500 POUNDS PER SQUARE INCH IN THE PRESENCE OF BLACK COPPER-CHROMIUM OXIDE CATALYST, SAID CATALYST BEING PRESENT IN AN AMOUNT IN EXCESS OF ABOUT 50% BY WEIGHT OF SAID TARTARIC ACID ESTER, AND RECOVERING ERYTHRITOL FROM THE RESULTING MIXTURE. 